Adaptive equalization and regeneration system

Abstract

An adaptive equalization and regeneration system is provided for accurately reconstructing a received data pulse train which has been degraded with respect to amplitude and instantaneous frequency. The system comprises an equalizer which responds to a control signal to provide a variable gain function for the received signal and output an equalized signal, digital phase lock logic for receiving and extracting timing information from the equalized signal, a regenerator for matching the timing information with the equalized signal to reconstruct the received data in its originally transmitted form, and control circuitry for providing the control signal to the equalizer. The control signal adjusts the slope of the equalizer gain function so as to minimize amplitude and instantaneous frequency degradation at the equalizer output. The system includes a mechanism to detect and calculate total signal degradation at the equalizer output. Control logic is used to identify the slope of the equalizer gain function at which total signal degradation is minimized. The control signal, which corresponds to this identified slope, is applied to the equalizer in real time to maintain minimum total signal degradation at the equalizer output.

We claim: 
     
       1. An adaptive equalization and regeneration system for reconstructing a signal received in the form of a data pulse train which has been degraded with respect to amplitude and instantaneous frequency, comprising: an equalizer for providing a variable gain function for said received signal and outputting an equalized signal, said equalizer gain function being varied in response to a voltage level applied to said equalizer to vary said equalizer gain function and increasing directly as a function of the frequency of said received signal, said voltage level varying the slope of said gain function, said gain function having a slope determined by a change in gain with respect to a change in said frequency;   digital phase lock logic for receiving said equalized signal and outputting timing information obtained from said equalized signal;   a regenerator for receiving said equalized signal and said timing information and matching said timing information with said equalized signal to reconstruct the received data essentially in its originally transmitted form; and   control circuitry connected to said equalizer for detecting variances in amplitude and instantaneous frequency in said equalized signal and for outputting said voltage level signal to said equalizer to vary said equalizer gain function in response to said detected variances, said control circuitry including control logic for (i) adding said variances in amplitude and instantaneous frequency in said equalized signal to provide a total signal variance, and (ii) determining the slope of said equalizer gain function at which said total signal variance is a minimum.   
     
     
       2. An adaptive equalization and regeneration system for reconstructing a signal received in the form of a data pulse train which has been degraded with respect to amplitude and instantaneous frequency, comprising: an equalizer for providing a variable gain function for said received signal and outputting an equalized signal, said equalizer gain function being varied in response to a control signal and increasing directly as a function of the frequency of said received signal, said gain function having a slope determined by a change in gain with respect to a change in said frequency;   digital phase lock logic for receiving said equalized signal and outputting timing information obtained from said equalized signal;   a regenerator for receiving said equalized signal and said timing information and matching said timing information with said equalized signal to reconstruct the received data essentially in its originally transmitted form;   control circuitry connected to said equalizer for detecting variances in amplitude and instantaneous frequency in said equalized signal and for outputting said control signal to said equalizer to vary the slope of said equalizer gain function, said control circuitry including control logic for (i) adding said variances in amplitude and instantaneous frequency in said equalized signal to provide a total signal variance, and (ii) determining the slope of said equalizer gain function at which said total signal variance is a minimum;   an automatic gain control circuit which is connected to said equalizer and which automatically controls an amplifying gain of said received signal to output an amplified signal to said equalizer; and   a peak detecting and averaging circuit comprising (i) a peak detector connected to said equalizer for sensing peak values of individual pulses in the data pulse train and for outputting said peak values, and (ii) a peak averager connected to said peak detector for receiving and averaging said peak values and for outputting an average value of said peak values to said automatic gain control circuit.   
     
     
       3. The system of claim 2, wherein said control circuitry includes (i) circuitry to calculate said variances in instantaneous frequency in response to said timing information output by said digital phase lock logic, and (ii) circuitry to calculate said variances in amplitude in response to said peak values sensed by said peak detector. 
     
     
       4. The system of claim 3, wherein said control logic determines the slope of said equalizer gain function at which said total signal variance is minimized and calculates said total signal variance for a plurality of values of said slope of said equalizer gain function. 
     
     
       5. The system of claim 4, wherein said control logic calculates said total signal variance incrementally in steps for said plurality of values of said slope. 
     
     
       6. The system of claim 5, wherein said incremental steps are dependent on data rate and data transmission medium, and are between the range of 0.003 dB/MHz to 0.010 dB/MHz. 
     
     
       7. An adaptive equalization and regeneration system for reconstructing a signal received in the form of a data pulse train which has been degraded with respect to amplitude and instantaneous frequency, comprising: an equalizer for providing a variable gain function for said received signal and outputting an equalized signal, said equalizer gain function being varied in response to a control signal and increasing directly as a function of the frequency of said received signal, said control signal varying the slope of said gain function, said gain function having a slope determined by a change in gain with respect to a change in said frequency;   digital phase lock logic for receiving said equalized signal and outputting timing information obtained from said equalized signal;   a regenerator for receiving said equalized signal and said timing information and matching said timing information with said equalized signal to reconstruct the received data essentially in its originally transmitted form;   control circuitry connected to said equalizer for detecting variances in amplitude and instantaneous frequency in said equalized signal and for outputting said control signal to said equalizer to vary said equalizer gain function in response to said detected variances, said control circuitry including control logic for (i) adding said variances in amplitude and instantaneous frequency in said equalized signal to provide a total signal variance, and (ii) determining the slope of said equalizer gain function at which said total signal variance is a minimum; and   an automatic gain control circuit which is connected to said equalizer and which automatically controls an amplifying gain of said received signal to output an amplified signal to said equalizer.   
     
     
       8. A method of reconstructing a signal received in the form of a data pulse train which has been degraded with respect to amplitude and instantaneous frequency, comprising the steps of: providing a variable equalizing gain for said received signal and outputting an equalized signal, said equalizing gain being varied in response to a control signal and increasing directly as a function of the frequency of said received signal, said equalizing gain defined by a function having a slope determined by a change in gain with respect to a change in said frequency;   controlling an amplifying gain for said received signal to output an amplified signal, prior to providing a variable equalizing gain for said received signal, by sensing peak values of individual pulses in said equalized signal and averaging said peak values;   providing said control signal using circuitry for detecting variances in amplitude and instantaneous frequency in said equalized signal, adding said variances in amplitude and instantaneous frequency to provide a total signal variance, determining said slope of said gain function at which said total signal variance is a minimum, and outputting said control signal to alter the slope of said equalizing gain function in response to said variances;   extracting timing information from said equalized signal and outputting said timing information to a regenerator for receiving said equalized signal and said timing information; and   matching said timing information with said equalized signal to reconstruct the received data essentially in its originally transmitted form.   
     
     
       9. The method of claim 8, wherein said step of providing said control signal includes the steps of calculating said variances in amplitude in response to said sensed peak values, and calculating said variances in instantaneous frequency in response to said extracted timing information. 
     
     
       10. The method of claim 9, wherein said step of providing said control signal includes providing control logic for determining the slope of said equalizing gain function at which said total signal variance is minimized, and for calculating said total signal variance for a plurality of values of said slope of said equalizing gain function. 
     
     
       11. The method of claim 10, wherein said control logic calculates said total signal variance incrementally in steps for said plurality of values of said slope. 
     
     
       12. The method of claim 11, wherein said incremental steps are determined by the rate at which and the transmission medium over which said data pulse train is transmitted and are between the range of 0.003 dB/MHz to 0.010 dB/MHz. 
     
     
       13. The method of claim 10, wherein said step of determining the slope of said equalizing gain function at which minimum total signal variance occurs includes the steps of: selecting a first value of slope of said equalizing gain function and calculating said total signal variance at said first selected value;   selecting a second value of slope of said equalizing gain function and calculating said total signal variance at said second selected value;   storing and comparing said total signal variances calculated at said first and second slope values;   selecting additional values of slope of said equalizing gain function in response to said comparison, and calculating said total signal variances at said selected additional values until a minimum total signal variance is identified.   
     
     
       14. A method of reconstructing a signal received in the form of a data pulse train which has been degraded with respect to amplitude and instantaneous frequency, comprising the steps of: providing a variable equalizing gain for said received signal and outputting an equalized signal, said equalizing gain being varied in response to a control signal and increasing directly as a function of the frequency of said received signal, said equalizing gain defined by a function having a slope determined by a change in gain with respect to a change in said frequency;   providing said control signal using circuitry for (i) sensing peak amplitudes in the equalized signal, (ii) detecting variances in said peak amplitudes and variances in instantaneous frequency in said equalized signal, and (iii) outputting said control signal to alter said equalizing gain function in response to said detected variances in peak amplitudes and instantaneous frequency;   extracting timing information from said equalized signal and outputting said timing information to a regenerator for receiving said equalized signal and said timing information; and   matching said timing information with said equalized signal to reconstruct the received data essentially in its originally transmitted form.   
     
     
       15. The method of claim 14, wherein said control signal alters the slope of said equalizer gain function, and wherein said step of providing said control circuitry includes the steps of (i) adding said variances in amplitude and instantaneous frequency in said equalized signal to provide a total signal variance, and (ii) determining said slope of said gain function at which said total signal variance is a minimum. 
     
     
       16. An adaptive equalization and regeneration system for reconstructing a signal received in the form of a data pulse train which has been degraded with respect to amplitude and instantaneous frequency, comprising: an equalizer for providing a variable gain function for said received signal and outputting an equalized signal, said equalizer gain function being varied in response to a control signal and increasing directly as a function of the frequency of said received signal, said gain function having a slope determined by a change in gain with respect to a change in said frequency;   digital phase lock logic for receiving said equalized signal and outputting timing information obtained from said equalized signal;   a regenerator for receiving said equalized signal and said timing information and matching said timing information with said equalized signal to reconstruct the received data essentially in its originally transmitted form; and   control circuitry connected to said equalizer for (i) sensing peak amplitudes in the equalized signal, (ii) detecting variances in said peak amplitudes and variances in instantaneous frequency in said equalized signal, and (iii) outputting said control signal to said equalizer to vary said equalizer gain function in response to said detected variances in peak amplitudes and instantaneous frequency.   
     
     
       17. The system of claim 16, wherein said control signal varies the slope of said equalizer gain function, and wherein said control circuitry includes control logic for (i) adding said variances in amplitude and instantaneous frequency in said equalized signal to provide a total signal variance, and (ii) determining the slope of said equalizer gain function at which said total signal variance is a minimum. 
     
     
       18. A method of reconstructing a signal received in the form of a data pulse train which has been degraded with respect to amplitude and instantaneous frequency, comprising the steps of: automatically controlling an amplifying gain for said received signal to output an amplified signal,   providing a variable equalizing gain for said amplified signal and outputting an equalized signal, said equalizing gain being varied in response to a control signal and increasing directly as a function of the frequency of said amplified signal, said control signal altering the slope of said equalizer gain function, said equalizing gain defined by a function having a slope determined by a change in gain with respect to a change in said frequency;   providing said control signal using circuitry for (i) detecting variances in amplitude and instantaneous frequency in said equalized signal, (ii) adding said variances in amplitude and instantaneous frequency in said equalized signal to provide a total signal variance, (iii) determining said slope of said gain function at which said total signal variance is a minimum, and (iv) outputting said control signal to alter said equalizing gain function in response to said determined slope;   extracting timing information from said equalized signal and outputting said timing information to a regenerator for receiving said equalized signal and said timing information; and   matching said timing information with said equalized signal to reconstruct the received data essentially in its originally transmitted form.